Method of and apparatus for drying wood veneer



Feb. 16 1926.

.METHOD OF AND APPARATUS FOR DRYING WOOD Filed Dec. 20, 1\9\22 A. ELMENDORF limmlhl Hlmllllh: Il

VENEER 2 Sheets-Shea Q N ,Tfn/infor:-

Feb. 16 1926. 1,573,379

. A. ELMENDORF METHOD OFAND APPARATUS FOR DRYING WOOD VENEER Filed Dec. 20, 1922 2 Sheets-5h80?, 2

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Patented Feb. 16, 1.926.,

UNITED STAT-Es PATENT OFFICE.

ARMIN ELMENDORF, OF CHICAGO, ILLINOIS.

METHOD AND APPARATUS FOR IJltYIlTGr WOOD VENEER.

Application led December 20, 1922. Serial No. 607,927.

`being had to the accom anyingdrawings,

which form apart of this specification.

The common method of handling wood veneer is to cut or tear it intosheets as it is formed from the log, the sheets being then dried and reaching the consumer in-what should be a Hat dry state. There are several common methods of drying, namely, between hot plates, between rolls in a heated chamber, and in kilns. It is very seldom that a sheet of veneer emerges from the ordinarydrying process without being warped and cracked. Therefore, although the ordinary drying methods are comparatively slowand costly,they do not result in the production of uniformily fiat, sound sheets, even though the sheets at the beginning of the drying processes may have been flawless.

When veneer is cut from the log it is in ajwet state, that is, a state in which the moisture content is above what is known as the ber saturation point. As long as the moisture content remains above the saturation point there -is substantially no expansion or contraction` of the veneer as the amount of moisture increases or decreases.

As soon as the moisture content drops below the saturation point, in the drying of the veneer, contraction across the Vgrain begins. Consequentlyywhen veneer is dried below the saturation point by passing it through a series of rolils, special provision must be made'to compensate for the contraction of the veneer in orderto prevent Vtearing the sheet or strip in two. Furthermore, since wood veneer possesses only a small degree'of tensile strength across the grain, which 1s in the direction` of the length of the strip or sheet as it is cut from.

the lo'g, provision must bemade to feed the veneer through -the .drying rolls in vsuch a way'thatthere be little or no tension result- -ing from the feeding means, quite apart from the tension which lmight be set up due to the shrinking or contracting of the material.

The object of the present invention is to p roduce a simple and novel process for effectually and economically drying wood veneer, the drying taking place while the veneer is being unwound from one roll and Woundup on another, without danger of tearing the veneer and in such a mannerl that the dried product will be flat and unwarped.

A further object of the present .invention is to produce a simple and novel machine or apparatus for carrying out my improved method.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but for a full, understanding of my invention and of its objects and advantages reference may be had to the following detailed description taken in connection with the accompanying drawings, wherein:

Figure l is a longitudinal vertical section through a preferred form of apparatus for carrying out my invention;

Fig. 2 is a section taken approximately on line 2 2 of Fig. l;

Fig. 3 is a View similar to Fig. l, showing only a fragment ofthe machine, with one of the elements adjusted to a diferent position from that which it occupies in Fig. l;

Fig. 4 is a View similar to Fig. l, showing a modied form of apparatus; and

Fig. 5 is a section taken approximately on line 5 5 of Fig. 4.

vReferring to Figs. l to 3, inclusive, l, 2, 3 and 4 represent parallel horizontal rolls. The number of rolls will of course depend upon the nature of the work to be done and upon Whether or not the drying operation is to be completed by a single passage of the veneer through the machine, or by passing the veneer through the machine more than once. However, since the principle of my invention does not' depend upon these details I shall, for the sake of brevity, con- 'ne the detailed description to the specific rolls with which they co-operate. At opposite ends of the group of rolls just described are feed rolls 6 and 7 lying parallel with the other rolls and of the same diame-l ter as the latter. The rolls are all driven at the same speed, but each roll is rotated in the opposite direction from the direction of rotation of the adjacent roll or rolls. This may be done in' any suitable manner, as, for example, by means of a sprocket chain drive 8. Above the rolls 6 and 7 are shafts or drums 9 and 10, respectively, mounted for rotation and bodily vertical movements im suitable stationary guides 11 and 12 fixed to the frame 13 of the machine. A strip or long sheet of veneer A wound up on the shaft or roll 9, in a wet state, is placed in t-he machine so as to rest .upon the feed roll of the operation dropping down on this flange or shelf and being guided thereby 'into the trough of the steam chest and underneath roll 1. The rolls 1, 2,' 3 and 4 are preferably covered with a blanket 15 or other absorbent material which will take up the moisture driven out of the veneer by the heat of the steam chest and, after being carried clear of the veneer, permit the moisture to be driven off again. Between the first steam chest and the roll 2 is arranged a guide 16, along which the veneer travels so as to be introduced between the upper half of the roll 2 and the stem chest overly-vv ing the latter. The guide, together with the adjacent portion of the first steam chest. preferably forms a more or less sinuous surface, so that the distance along the same from the first drying roll to the second is greater than it would be if a flat shelf or platform were employed. Above the guide 16 is a co-operating guide 17 having a sinuous working face extending between the first heating roll and the second steam chest. Between the rolls 2 and 3 are lower and upper guides 18 and 19 similar to guides 16 and 17 but oppositely disposed so as to feed the work down from the top of the second roll to the under side of the third roll. Be-

tween the third and the fourth drying rollsl are lower and upper guides 20 and 21, identical withthe guides 16 and 17. Between the last drying roll and the feed roll 7 is an inclined guide 22 extending from near the top of the drying roll downwardly underneath the roll 7 and upwardly past the opposite side of that roll so as to cause thefree endL of the veneer, after passing thev dryin'g rolls, to travel underneath `the 'roll '7 and then to the upper side thereof, where it may be wound up on the receiving ,shaft or drum 10. After the free end of the veneer has been attached to the receiving end or shaft, the latter will be frictionally. driven from the feed roll 7 in a direction -to cause the veneer to be wound'up as it reaches e the dischargeend of the machine, the shaft or drum rising in the guides 12 as the nurnber of layers .o'f veneer thereon increases,

The guides 16 to 22, inclusive, need not extend continuously throughout the lengths of the rolls, but may be made in sectins so as to form, in effect, a series of parallel separated tracks or channels between each pair of rolls; thus exposing both sides of the veneer to atmosphere in the spaces between consecutive rolls and permitting steam-"t escape therefrom directly into the air. ,Y lVhenla full roll of veneer is placed-into the right hand end of the machine, as viewed in Fig. 1, so as to rest on the feed roll 6, and the machine is set in operation, the veneer will be unwound without thel exertion of any pull thereon and will be fed down underneath the first heating roll, A

which presses it against the steam chest and, through frictional engagement with the veneer, feeds it along at the same speed, as that at which it is delivered from the roll 6. As the free end of the veneer emerges from beneath the first heating roll, it enters betweenthe sinuous guides 16 and 17, and is pushed ahead until it reaches the second heating roll,\which in turn acts as a feeding means. Inthis way the veneer is pushed ah'ead and driven along through'frictonal engagement with the heating rolls until it reaches the discharge end of the' machine, where it lwill bewound up, as heretofore explained. The veneer does notlit closely in the space between -the sinuous guides of each set, but these guides are spaced far enough ,apart so as to' permit considerable freedom of movement ofthe veneer. In other'words, an appreciable amount of slack is formed in the veneer between each two consecutive heatingvrollsand, if there -should be such shrinking of the veneer as would place the veneer under sufiicienttension, if the veneer extended tangentially between the rolls, to cause the veneer to be torn, the creation of such a tension and the tearing of the veneer will be prevented by the possibility of simply taking up slack in the veneer' between the rolls. If desired, the guides may be so constructedrthat they may be opened so as to permit all of the slack to be taken out of the veneer and permit it, if necessary, to straighten out completely between consecutive rolls. In the arrangement shown, the upper guide members 17, 19 and 21, are supported upon eccentrics 25,' which may be turned so as to raise these guides from posif tions indicated in Fig. 1 to a position corremachine-in atrue flat condition.

sponding to that shown in Fig. 3, in which latter-figure the veneer is shown as extending in a flat-conditionbetween two of the rolls. Y

It will be seen that the veneer'is bent alter- -nately in opposite directions, such that the libres in the veneer are causedI to remain straightv or, if warping has occurred, are first straightened and then caused to remain straight, whereby the veneer 'will Aleave the Itr will also be seen that the heat is applied first to one side of the veneer, and then to the other, thus avoiding the danger of case-hardening' only one side and, at the same time securing a more eiiicient application of the heat than is' possible where` the transfer ofthe heat V y lReferring to these figures, 3l and 32 represent' rtwo co-operating feed rolls, of which there may be'any desired number of pairs; six such pairs being shown, `suitably distributed along asupporting frame 33. The

. lower rolls are provided with a series of circumferential grooves 34` distributed lengthwise thereof. fA series'of long strips o1'l thin bars 35 of spring steel or other suitable springy ,material extends lengthwise through. the group of feed rolls, each bar llying in one of the grooves of'each of the lower feed rolls. The'bars are fastened at one end, as indicated at 36, to the frame of the machine, whilethe other ends of the bars are free. Between the upper'rolls are placed suitable guides 37 conveniently made in the form of bars long enough to extend from one set ofrolls to the neXt,-lying directly above the strips or bars 35, and curved upwardly between the ends. Located midway between each pair of feed rolls is a roller 38 underlying thexstripsor bars 35 and having its axis parallel with the axes of the feed rolls'. The rollers38 are supported on the upper ends of 'standards 39 extending through and, screw-threaded into suitable' stationary pedestals 40. 0n the lower end of .each standard uis .aworm wheel 41, meshing with a suitable lworm 42 on a longitudinal shaft `n4:3. There are preferably two;` sets 'of Supporting standards, one at each end ofthe rollers,- and therefore two worm shafts.4 Either worm shaft may be rotated in any suitable man-- ner, the other being 'caused to rotate bymeans of a belt or chain 44 passing over suitable wheels or pulleys45 fixed tothe two worm shafts. The parts are so propor- 'direction and at the same speed.

tioned that when the rollers aie' raised they bend the strips 35 in the upward direction,

so that` these strips, with the overlying guides 37, form curved passa es through which the veneer must travel om one set of rolls to the next. 'When it is desired to enlarge these passages, `the rollers are simply lowered, permitting the bars 35 to straighten, and thereby permitting the veneer to extend straight across from one 'set of rolls to the next, if desired.

The veneer to be dried is wound on a drum or shaft 9, as in the other form of machine, the roll of veneer being allowed to rest on Y the upper feed roll of the first set vand moving down by gravity inthe guidingfbearings l1 as the veneer is unwound and the diamf eter of the roll decreases. At theother end y of the machine the veneer is wound up on a shaft or drum 10, as in the other machine.

The feed rolls and the guides are enclosed in a housing 46 containing steam pipes 47y and suitable fans'fiS for blowing the hot air acrossfthe veneer as it is traveling through the machine.

Either or both rolls of each setl of rolls` may be driven. In the arrangement shown, the upper rolls, alone, re adapted to be driven by means of a sp ocket chain drive 4.9 connecting all of the rolls together and adapted to rotate the upper rolls in the same It will be noted that the rolls in either machine may first he driven in one direction and then in the other, causing the veneer to be passed through the machine irst'in one direction and then in the other, without removing it. This'makes it possible to use a machine much smaller than would be necessary to dry the veneer during a single passage therethrough, since the veneer need only be run back and forth through the machine a sufficient number of times to dry it.

While I have illustrated and described in detail two satisfactory forms of machine, the lirst form adapted particularly for drying thin` veneer and the second form adapted particularly for drying heavy veneer, yby which my improved method may be carried out, I do not desire tobe limited to such details, but intend to cover all forms, arrangements and series of steps which come within the definitions of my invention constituting the appended claims.

I claim:

1. The method of drying veneer 'which consists in passing it through successive feeding devices adapted to feed the veneer lat a uniform speed, applying heat to' thev tion of the said first feed roll andbexadvanced toward the second feed roll, causing the veneer to take a curved form between adjacent feed rolls, .and lapplying heat during the passage of the veneer. 3. The method of drying veneer which consists in passing it through successive feeding devices adapted to feed it at a uniform speed, applying heat to the veneer dur-v -ing its passage, controlling the advancing veneer to cause it to take a curved shape between consecutive feeding devices, and thereafter permitting'the curved portions to fiat-l ten out more or less jas shrinking occurs.

4. The method of drying veneer which consists inpassing it through successive feeding 'devices adapted to feed it at a uniform speed, applying heat to the vencer during its passage, causing the veneer to pass between curvedguides inthe spaces between cation.

consecutive feeding devices, and spreading said guides apart as shrinkage occurs'in order to provide slack to compensate for such shrinkage. n

5. The method of drying Wood veneer which consists in bending it alternately in opposite directions parallel with the libres so as to keep the libres straight and applying heat first to one side thereof and then to the other side. 6. A machine comprising a series of hori- Zontal rolls rotatable at the same speed, each roll being rotatable in the opposite direction from the immediately 'adjacent roll or rolls,

steam chests co-operating with and'having 4 curved surfaces lylng near said rolls, some of the chests being above certain of the rolls and the other chests being below the other rolls.

In testimony whereof I. sign this specifi- ARMIN ELMENDORF. 

